Rubber composition and method of producing the same.



WTTED %TATE% PATENT @FETQE.

JOHN M. WEISS, OF NEW YORK, N. Y., ASSIGNOR TO THE BARRETT COMPANY, ACORPORATION OF NEW JERSEY.

RUBBER COMPOSITION AND METHOD PRODUCING THE SAME.

No Drawing.

' To all whom it may concern Be it known that 1, JOHN M. Weiss, acitizen of the United States. residing at 210 West'110th street, NewYork, in the county of New York and State of New York, have inventedcertain new and useful Improvements in Rubber Compositions and Methodsof Producing the Same, of which the following is a specification.

This invention relates to rubber products and compositions, and moreparticularly to dense and non-porous vulcanized products andcompositions of improved (ll-electricproperties having incorporatedtherewith, prior to the vulcanization, a semi-solid to solid bitumenobtainable by the destructive distillation of coal tar and coal tarpitch.

In the destructive distillation of coal tar and of coal tarpitch, thereis obtained, at the final stage otlevolution of condensable distillate,a semi-solid to solid product of characteristic composition andproperties. This product is bituminous in character and may properly bereferred to as a bitumen, within the standard definition of the AmericanSociety for Testing Materials. This bitumen is an extremely high boilingproduct and undergoes partial decomposition if distilled underatmospheric pressures. It varies in color from a dark brown to a clearcherry red product, and can readily be obtained in the form of a lightcolored product relatively free from black or brown coloration and freefrom free carbon. It is very resistant to dilute acids and alkalis, andit is soluble in such common solvents as benzol, and coal tar naphthas,etc.

This semi-solid to solid bitumen, thus obtainable by the destructivedistillation of coal tar and coal tar pitch, may be melted,

by the application of heat, and may have a meltin point. varying, forexample, from around 110 to 115 F. or lower-,Up to around 145 to 155 F.,or eVen as high as 190 F. or higher, the melting point being determinedaccording to the Cube melting point method for bituminous materialsdescribed by S. R. Church in the Journal of Industrial and EngineeringChemistry for April, 1911. The specific gravity of the bitumen isunusually high certain samples thereof which have been examined showingspecific gravities, at about 155 (1., from Specification of LettersPatent.

Patented Oct. 22, 1918.

around 1.233 or even lower up to around 1.25 or higher.

The bitumen moreover has remarkable dielectric properties. Samples ofthe bitumen have been found to have as high a di-electric strength as550 to 700 volts per mil, or even higher.

This bitumen, with its characteristic composition and properties, isobtainable from coal tar or coal tar pitch by difierent'methods ofprocedure. It may thus be obtained as the last fraction of thecondensable distillate in the straight distillation of coal tar to coke,this last. fraction being properly cut so that the bitumen issubstantially free from greases and lower boiling components. Again,where the distillation of the coal tar has proceeded only to'theformation of coal tar pitch, this pitch may be subjected to aredistillation, for. example, in a coke oven, and the bitumen obtainedtherefrom at the end of the destructive distillation a d at the finalstage of evolution of con- .lensable distillate as above described. Thefractions of the distillate which come over before the semi-solid andsolid bitumen frequently carry with them appreciable amounts of thebitumen. and the bitumen may be obtained from these distillates by asuitable redistillation.

It will be evident that various specific methods of procedure may befollowed, and that different types of apparatus may be used, in theproduction of the bitumen by the destructive distillation of the coaltar or coal tar pitch.

The bituminous substance or bitumen thus obtainable will be hereinafterreferred to, in the specification and in the appended claims, simply asthe bitumen, or as the semi-solid to solid bitumen obtainable by thedestructive distillation of coal tar pitch.

Where the bitumen is initially produced in an impure state it may befurther purified, by distillation or otherwise, for example, by steam orvacuum distillation. If distilled under ordinary pressures the bitumenundergoes partial decomposition, forming greasy bodies some apparentlyunchanged bitumen and coke residue, so that such distillation will notgenerally be feasible for purification of the impure bitumen; but thecomposition tion with corresponding modification of the vulcanizationprocess, and with the production of a correspondingly modifiedvulcanized product.

The properties of the bitumen above referred to, such as its resistanceto alkalis and acids, its high specific gravity, and its unusualdi-electric properties, inhere, to a greater or less extent, in thevulcanized products in the production of which the bitumen is employed.The vulcanized products will thus be of increased density due to thehigh specific gravity of the bitumen itself, while the di-electricproperties of the rub ber compositions and products will be similarlybenefited by the incorporation of the bitumen therein.

The compositions and products of the present invention are of especialvalue for purposes Where a light colored product is desired. It is wellknown that coal tar pitch, and the usual asphaltic and bituminouscomponents of rubber mixtures, are of a black color, and correspondinglydarken the vulcanized products in the production of which they areemployed. The bitumen employed in the process of the present invention,however, when properly prepared and purified, is substantially free fromobj ectionable black coloration, and has a pleasing clear and usuallycherry red coloration, which imparts to the compositions and products,in the manufacture of which the bitumen is employed, a slight butunobjectionable tint. Such vulcanized products and compositions,accordingly, may be used Where light colored rubber products are desiredand where black products would be undesirable. The advantage oflightness in color, as will be evident, will be an added ad vantage, inaddition to the other desirable properties imparted to the vulcanizedproducts by the bitumen.

The bitumen may, however, be used to advantage in the production ofcompositions or products where light color is not of importance, andWhere it may even be desirable to produce a dark or black product. Insuch cases the other advantages of the bitumen 'Wlll be retained. Forsuch purposes, the

bitumen itself need not be entirely free from dark coloration, but mayeven have a pronounced dark brown color, although, as above pointed out,it can readily be produced substantially free from objectionable darkcoloration.

In the production of high grade rubber products and compositions, gradesof rubbers, such as Para or plantation rubbers, will usually beemployed. For other purposes, other rubbers of an inferior grade may beemployed. In any case, the composition or mix may contain fillers ofvarious kinds, or pigments, or other specific substances or reagents,such as, for example, zinc oxid, lithopone, etc., for hardening therubber or imparting special properties to the resulting finalcomposition or product.

The vulcanization process can be carried out by the incorporation of anappropriate amount of sulfur either with or Without other agents forpromoting or modifying the vulcanization process. For hard 7 rubberproducts more sulfur will be employed than for soft rubber products. thevulcanizing agent, as well as the time, temperature and pressure ofvulcanization, will vary with the nature of the compositiqn and with thecharacter of the product which it is desired to produce, 0. whet-her theproduct is to be a soft vulcanized product or a hard rubber product.

The bitumen may be incorporated with the rubber and other constituentsof the mix in any suitable manner. The mixing operation will be promotedby heating the rubber on the mixing mill to such a temperature that thebitumen will become plastic or even liquid upon contact with it, carebeing taken, however, to avoid the use of excessive heat that mightdestroy the nerve of the rubber. When the bitumen has been ground up orcomminuted it 'may be added in this form along with the otheringredients of the mix and incorporated during the rolling or mixingoperation. The bitumen may also, in some cases, be incorporated withadvantage by the use of its solutions, and by uniform distribution ofsuch solutions throughout the rubber, by the use of solutions of thebitumen in solvents which are likewise solvents of the rubber itself.This will be of especial advantage in the production of so-calledsolutions of rubber such as are used for waterproofing fabrics and thelike, since the bitumen and the rubber may be dissolved in commonsolvents and a 'uniform distribution of the bitumen and rubber therebypromoted. Where such rubber solutions are made and used, the solvent maybe subsequently removed, leaving the bitumen intimately combined withthe rubber and other constituents of the rubber composition, and thevulcanization may be then effected in any suitable manner, as by theso-called cold vulcanization process, making use of sulfur chlorid, orby the Well-known hot room process, or otherwise.

the higher The amount of I escapee It will be understood that so-calledwaste or reclaimed rubber may be employed in the production of thecompositions and products of the present invention, for example, inadmixture with the higher grades of rubber, and the waste or regeneratedrubber will be modified by the vulcanization thereof, in admixture withthe bitumen.

Vulcanized products may be similarly prepared by the use of so-calledvulcaniz'able oils, which, upon vulcanization, produce socalled rubbersubstitutes. The hereinbefore described bitumen may, with similaradvantages to those above referred to, be incorporated in suchcompositions, prior to their vulcanization. It will be evident also thatvulcanizable oils may be incorporated with rubber in the preparation ofcomposite vulcanized products in the production of which the bitumen isalso utilized.

The invention will be further illustrated by the following specificexamples of compositions made in accordance therewith.

No.1 No.2

Para rubber 76.2 53.

Sulfur 9.52% 9.66%

Magnesia 4.76% 4.5 Bitumen (hereinbefore described) 9.52% 32.84%

Such mixtures may be subjected to vulcanization, for example, for aperiod of thirty minutes at a steam pressure of f0rtyfive (45) pounds;but the time and pressure (and corresponding temperature) may varywithin rat-her wide limits, depending upon the particular use for whichthe product is desired.

Where hard rubber productsare desired a much larger percentage of sulfurwill e used and the vulcanization process will be correspondinglymodified. So also, various fillers or compounding materials may be used,depending upon the purposes for which the resulting products aredesired.

The products thus produced will be of improved density and dielectricproperties due to the hereinbefore described bltumen employed in theirproduction. Where the bitumen is of cherry red color the products willbe light colored products, substantially free fromdark coloration, ifthe rubber and other ingredients employed are themselves free from darkcoloration. At the same time, the products or compositions will have theother characteristic properties imparted to them by the bitumen.Inasmuch as the bitumen is free from dark coloration it will likewise befree from free carbon, which, if present, would modify the electricalproperties of the compositions or products. Because of the absence offree carbon in the bitumen, and because of the other desirableproperties imparted to the compositions and products by the bitumen,these compositions and products will be of value for electricalinsulationpurposes.

The slight reddish tint which may be imparted to compositions made withthe hereinbefore described bitumen may even be of advantage for certainpurposes, for example, for dental rubber where a reddish coloration isdesired.

The light coloration of the bitumen moreover, makes it possible toproduce rubber compositions and products of various colors, by theaddition of various pigments and coloring materials, without thedisadvantages incident to the use of black ingredients such as coal tarpitch and the like, or carbonaceous components of an essentially blackcharacter.

The amount of the hereinbefore described bitumen which may be used, inthe production of the improved compositions and products of the presentinvention, may vary within rather wide limits, as will be evident fromthe specific examples above given, and depending on such considerationsas the nature of the mix, the components of which the mix is made up,the object for which the product is desired, and the nature of thevulcanization process, whether hot or cold, and whether for theproduction of hard or soft rubber products.

While the invention has been more particularly described in connectionwith vulcanized compositions and products, yet it will be understoodthat unvulcanized compositions and products may be similarly produced bythe incorporation therein of the bitumen, and'that these compositionsmaybe employed without vulcanization or for purposes where vulcanization isto be subsequently effected, for example, in the coating of fabric wherethe coating is to be subsequently vulcanized. For certain purposesunvulcanized compositions of a more or less plastic character aredesired and such-compositions are intended to be included within themore comprehensive claims appended hereto. Such compositions, however,are to be distinguished in certain important respects from thevulcanized compositions and products which are more specificallyclaimed.

I claim:

1. The method of producing vulcanized compositions and products, whichcomprises incorporating with a vulcanizable ingredient of thecomposition to be vulcanized, a semisolid to solid bitumen obtainable bythe destructive distillation of coal tar pitch, and v solid bitumen.obtainable by the destructive distillation of coal tar pitch. andsul'ijecting the composition to vulcanization; substantially asdescribed.

3. .\s new articles of manufacture. rubber compositions and productscontaining rubber and a semi-solid to solid bitumen obtainable by thedestructive distillation of coal tar pitch; substantially as described.

4. As new articles of manufacture, rubber compositions and products oflight color, containing rubber and a light-colored semisolid to solidbitumen obtainable by the de structive distillation of coal tar pitch;substantially as described.

As new articles of manufacture, vulcanized compositions and productshaving, incorporated therein prior to the vulcanization thereof asemi-solid to solid bitumen ob-' tainable by the destructivedistillation of coal tar pitch; substantially as described.

6. As new articles of manufacture. vulable by the destructivedistillation of coal tar pitch; substantiall as described.

8. As new articles of n'ianufacture. light colored rubber compositionsand products having incorporated therewith prior to vulcanizationthereof a. light colored semi-solid to solid bitumen obtainable by thedestructive distillation of coal tar pitch; substantially as described.

In testimony whereof I afllx my signature.

JOHN M. \VEISS.

